Studies by the United States-Environmental Protection Agency have found that approximately two-thirds of the leaks in underground storage tanks can be traced to failure of an underground piping system rather than to the tank itself. Specific locations include joints such as unions, elbows and couplings where two straight pieces of pipe are joined together, connections to underground equipment, and corroded steel pipes.
Also, structural failure in piping systems can occur when movements take place in tanks and/or piping systems due to to high water tables or settling ground movement. This is particularly true in the case of rigid fiberglass piping systems which are subject to cracking or outright structural failure.